Efficient Millimeter Wave Doherty PA Design Based on a Low-Loss Combiner Synthesis Technique

We report on a record-efficient 30-GHz 21-dBm differential Doherty PA designed in a 130-nm SiGe process. The output network is designed using a recently developed combiner synthesis technique. This technique enables impedance inversion and parasitic compensation to be integrated in one compact network. As a result, the combiner loss is reduced with 0.3-0.5 dB compared with a conventional Doherty combiner. The measured collector and power-added efficiencies at 6-dB back-off level are 30% and 24.3%, respectively, which further validates the advantages of the design technique.